making geom recognize cd changes

[Dominic Fandrey]

I'm trying to get geom to recognize atapi-cd changes in order to update the
labels. I'm concentrating my efforts on src/sys/dev/ata/atapi-cd.c. I have
tried to run acd_geom_attach and acd_geom_detach both directly and through the
geom queue from acd_tray, but there is no effect. Something about my approach
seems to be entirely wrong.

Please make sure to CC me, I'm not subscribed to this list.